The present invention relates generally to a method of and an apparatus for transferring a fast running ready-dried fibrous web having two longitudinal edges from one device and along a predetermined run to a subsequent device for performing an act or operation on the web. In a typical installation, the apparatus is installed downstream of a drying section of a papermaking machine, or in association with a rewinder or in a converting plant, for example.
One embodiment of the invention relates specifically to an apparatus for transferring a fast running ready-dried tissue web having two longitudinal edges from a drying section of a tissue paper making machine and along a predetermined run to a reel-up.
In this context, the term “tissue paper” is intended to include any grade of “soft crepe paper” or other paper for sanitary purposes, whether creped or not when used by a consumer.
The performance of a tissue machine is often limited by its dry end. Generally, the difference between a tissue machine with high efficiency and one with low efficiency is mainly caused by the performance of the dry end. In the dry end, several causes may result in web breaks, and the produced web may be partially rejected for unsatisfactory quality. However, with good control of the whole paper making process and use of the latest dry end technology it is possible to run a machine at both high speed and high machine efficiency.
The main factors affecting dry end machine efficiency are lost time with no paper on the reel, and the amount of paper rejected at paper breaks. On most high speed machines the paper web roll is kicked out at a paper break, because it is difficult to make a turn-up on a half size roll, and if the roll is small, the roll is rejected. Having this in mind, the dry end machine efficiency can be split up as follows.
Dry End Machine Efficiency:
Creping blade changes
Paper breaks including rejected paper in kicked out roll
Tail threading failures
Turn-up failures
Dry end cleaning (to avoid web breaks caused by dirt falling down)
Lost process control
Roll top waste and roll bottom waste
Roll bottom waste is caused by the paper web adjacent the reel spool having to be rejected and, similarly, roll top waste relates to the paper lost at the top of the roll during the kick-out phase, and/or by taking samples for testing and/or roll handling after the tissue machine.
In an efficiently operated machine, the threading of a new tail, after creping doctor blade changes and web breaks, does not take more than a few seconds. If the threader is out of adjustment, several minutes can be lost during each attempt to thread. Paper may plug the tail chutes and time consuming cleaning of the whole dry end may be required. The air chute threader is considered the most efficient and safest threader. There, the tail is transferred by compressed air in chutes, substantially as disclosed in U.S. Pat. No. 3,847,390 (Dixon), for example. Pneumatic tail threaders of other than chute type are disclosed in U.S. Pat. Nos. 3,999,696 and 4,014,487 (both Rehn et al.) and 4,923,567 (Liedes et al.).
The tail threaders may be mounted outside of any web stabilizers. Web stabilizers or flutter suppressors are disclosed in U.S. Pat. Nos. 4,321,107 (Page) and 3,650,043 (Overly et al.), for example. The design of the leading edge of a flat sheet stabilizer must be such that the boundary layer of air entrained by the web can escape on the top side of the stabilizer when the stabilizer is located above the predetermined run of the web. To maintain web control and prevent wrinkles, breaks and foldovers, the web tension must oppose the forces from disturbing air currents. Such currents originate from the machine room, the boundary layer of air, and the rotating rolls of the paper machine. The heat convection air flows are another source of disturbing air currents in the dry end.